Magnetic speedometer.



Patented sept. 10,'191'2.

A\ -v uw sa l sa E Si d 0 4 l: Si Si s E! UNITED STATES raTENT oEEioE.

JOI-IN K. STEWART, OF CHICAGO, ILLINOIS.

MAGNETIC SPEED OIVIETEIR.

Specification of Letters Patent. Patented Sept. 10, 1912,.

Application filed July 5, 1911.

Serial No. 636,896.

To all 'whom it may concern: y

Be it known that I, JOHN K. STEWART, a

.citizen of the United States, residing at effect of temperature changes, and thus to adapt the instrument to give true indication of speed at all ordinary temperatures.

It consists of the features and elements described and shown in the drawings as indicated in the claims.'

In the drawings :Figure' 1 is a top plan View of the instrument certain parts being broken away to show the interior construction. Fig. 2 is a vertical sectiontaken as indicated at line 2 2 on Fig. l. Fig. 3 is a vertical section taken as indicated at line 3-3 on Fig. 1. Fig. 4 is a detail plan view of an adjustable supporting plate for the non-magnetic element. Fig. 5 is a sectional detail taken as indicated at line 5 5 on Fig. l.

The instrument illustrated in the drawings comprises a shell, l, in which are mounted a speed-indicating device, a mileage recorder or odometer, and adjusting mechanism operating upon the speed indicator for correcting it, to compensate for the effect of temperature change upon its operation. The speed indicating device consists of a rotatably moiinted magnet, 2, connected by bevel Gearing 2, 3L with a driving shaft, 3, and czilculated'to cause limited rotation of a non-magnetic element, 4, mounted con; centrically with the magnet., 2, and biased to a definite position of rest by a spring, 5. As illustrated, the magnet, 2, is mounted on a carrier, 6, journaled upon an upstanding post, l, projecting from the bottom of the shell, l, and provided with ball bearings, 7. Surrounding th. magnet, 2, there is an annular space formed between the said magnet and an outer ring, 8, of soft iron, also secured to the carrier, 6. It will be understood that this arrangement of parts produces a.

magnetic eld in the annular space between the magnet, 2, and the soft iron ring, 8.

The non-magnetic element, 4, isshown as' constructed of two parts, namely, a fiat disk,

4, upon whose upper surface an indicating ring, 8. This non-magnetic element is provided with a hub, 4e, mounted fast upon a spindle 4d, which is journaled in jewel bearings, 4e andy 4f, respectively. 1

It is well understood that the operation of this type of instrument depends upon the efi'ect of the magnetic drag of the rotating magnet, 2, upon the non-magnetic element, 4, and it is also a matter of common knowledge that an increase of temperature, by decreasing` the electrical conductivity of the non-magnetic element, 4, tends to lessen the effectof the magnetic drag upon the said non-magnetic element, so that at a' given speed of' rotation of the magnet, 2, the disk, 4a, will not be rotated through so widean angle as it would be at a lower temperature, and since this angle is employed as an index of the speed which the instrument measures,

the accuracy of the instrument will be greatly impaired by a considerabletehange of' temperature from that atwhiclrthe instrument was originally calibrated. Since, however, the magneticdrag acts principally upon the fiange, 4b, of the non-magnetic element, 4, it is possible to compensatefor `this error, which would be introducefd with temperature changes, by varying the depth to which this fiange, 4, is int-ruded into the annular space between the magnet, 2, and

ment be calibrated at the highesttemp'erature at which it will probably ever be employed, and with the flan-ge, 4, extending its maximum distance into the annularfv space, it will only be necessary to partially withdraw the flange, 4", from the annular -the sof't iron ring, 8. Then, ifthe instrufrom the plate, 9, and the lower jewel, 4f, is supported upon an arm, 10a, extending from the plate, 10, through a longitudinalslot, 1b,`in one side of the post, 1, in the hollow interior of which the jewel, 4f, is contained. The spiral biasing spring. 5, has its inner end connected to the hub, f1, while its outer end is keyed in a lug, 9", extending from the upper plate, 9, so that the non-magnetic element, 4, is virtually carried between the plates, 9 and 10, absolutely independently of the magnet, 2.

For raising and lowering the element, 4t, with respect to the magnet, 2, there is provided a jack-screw, 13, journaled upright in the bottom of the shell, 1, with its threaded portion, 13a, engaging a threaded aperture, 10b, in the lower plate, 10. The middle portion of the screw is enlarged to form a worm wheel, 13b, and its lower end is provided with an applied flange, 13C, secured by a screw, 13d, and occupying the counter-sunk portion of the journal aperture in the shell, 1, thus serving, together with the enlarged portion, 13, to prevent movement ot' the screw in the direction of its axis. A worm shaft, 14, is journaled in the shell, with its worm, 14, meshing with the worm wheel, 13b, and by means of a pair of spiral gears, 15 and 1G, the shaft, 14, is connected for rotation with an operating spindle, 17, which extends outside the shell, 1; a second worm, 14h, cut upon the shaft, 14, meshes with a worm gear, 18, whose elongated hub, 18a, frictionally engages a spindle 19, by which is carried an index needle, 20. The needle, 20, is mounted to traverse a dial, 21, which is marked with a scale corresponding to a portion of a thermometer scale, indicating degrees of temperature.y From the foregoing description it will be seen that manipulation oit the knurled head, 17, of the operating spindle will cause rotation of the jack' screw, 13, and consequent movementof the plate, 10, along the threaded portion, 13, of the screw. The plates, 9 and 10, being tied together by the tubes, 11, will thus be moved bodily along the guide posts, 12, carrying the flange, 4", of the element, 4, up or down within the annular -spacc between the magnet, 2, and the soft iron ring, 8. Simultaneously, the index needle, 20, will be `moved around the dial, 21, indicating the l,tenxperature at which the instrument, as set, ,is thus adapted to give a true measurement lbf speed.

To facilitate the proper positioning of the index needle, Q0, when the instrument is originally calibrated, and also tov render it readily alterable in case the instrument sliduld need calibration at a later date, on

. account of' the aging of themagnet, Q, the

spindle, 1 9, is provided with a head, 19, having a screw driver slot, 19", by which the spindle may be engaged for turning it within the hub, 18a, of the worm gear, 18. This slotted head of the spindle, 19, is covered by the outer shell, 23, so as to be inaccessible under ordinary circumstances, to prevent tampering with the instrument by other than repair experts.

Convenience'is assembling the plates, 9 and 10, with the tubes, 11, is secured by providing the said tubes with laterally extending lugs, 11, at their upper ends, which are apertured and threaded to receive screws,

11", extending through the upper plate, 9.

The lower ends of the tubes, 11, extend into the lower plate, 10, andare rigidly secured thereto, and this much of the spindley carrier can be set in place in the' .rstruine at following the positioning of the magnet carrier, 6. Then, by inserting the jewel, 4f," and the spindle, 4d, together with the element, 4, and finally securing in place the top plate, 9, to which the spring, 5, is attached, the assemblage of the parts is readily completed. The 'face plate, 2,2, of the instrument which may then be applied, is pro .fi ded with a window, 22a, formed atene eige with an index point, 92", under which the dial, 4a, carrying its speed indicating scale, is moved by the ac tion of the magnetic drag upon the element, L1. Similar windows, 22 and 22d, are provided for the season and trip record scales of the odometer train, and the temperature dial which is traversedA by ythe needle, 20, is imprinted upori this plate.

I claim i 1. In a magnetic speedometer, in combination with a case, a magnet mounted for rotation in the case, a non-magnetic element having the form of an inverted cup mounted for rotation co-axially with the magnet and having its rim or flange encompassing the path of rotation of the magnet poles; a spin dle upon which said non-magnetic element is carried for such rotation, a frame and bearing carried thereby for the opposite ends of the spindle and means for moving the frame bodily in the direction parallel 'to the axis of the spindle for adjusting said non-magnetic element relatively to the magnet.

2. In a magnetic speedometer comprising a rotatably mounted magnet, and a movably mounted non-magnetic element extending into the field of said magnet; an index device; an element having a graduated scale coperating with said index; means f'or moving said non-magnetic element toward and from the magnet for varying the amount of its intrusion into the magnetic field thereof, and actuating connections from said means adapted to cause relative movement between said scale and index.

3. In a magnetic speedometer comprising a rotatably mounted magnet-carrier, a magnet and a soft iron ring positioned upon said carrier and separated by an annular space coaxial with the carrier; a non--magiietic element lia-ving the form of an inverted cup mounted for rotation coaxially with the carrier and having its rim intruded into the aforesaid annular space; means for moving said noli-magnetic element along its axis for varying the amount of the intrusion ont its rim into said annular space.

l. In a magnetic' speedometer comprising a case, a hollow post formed therein; a niagiiet journaled for rotation upon said post; a iionmagnetic element anda spindle therefor said spindle extending into the hollow interioi of the post; bearings for the upper' and lower ends of said spindle respectively; a traine within the case mounted for movenient parallel to the axis of the post and provided with a pair of lugs which support respectively the upper' and lower bearings oit' the spindle, and means for moving the frame within the case.

In a magnetic speedometer comprising a case, a hollow post formed therein; a inagnet journaled for rotation upon said post; a non-magnetic.element and a spindle therefor extending into the hollow interior of the` post; bearings for the upper and lower ends of said spindle respectively; a frame within the case mounted for movement par` allel-to the axis of the post and provided with a pair of lugs which support respectively the upper and lower bearings ofthe spindle; a jaclrscrew mounted for rotation within the case with its axis parallel to the axis of the post, the frame having a threaded aperture adapted to receive the threaded. portion of the jack screw, and gearing mounted on the case and adapted for ro-' tating the jaclrscrew.

6. In a magnetic speedometer comprising a case, a hollow post formed therein; a niagnet journaled for rotation upon said post; a non-magnetic element and a spindle therefor extending into the hollow interior of the post; bearings for the upper and lower ends ot' said spindle respectively; a frame wit-hin the case mounted for movement parallel to the axis of the ,post and provided with a pair of lugs which support respectively the upper and lower bearings'of the spindle; a jack screw mounted for rotation within .the case with its axis parallel to the axis of the post; the frame having a threaded aperture adapted to receive the threaded portion of the jack screw; gearing mounted on the case and adapted for rotating the jack screw; an

index, and an element having a. graduated scale cooperating with said index, and gearing arranged to cause relative movement between said scale and index, an element in the first of said gearings being connected for simultaneous rotation with an element in the other gearing for maintaining fixed relation between the movement of the two gearings.

7. In a magnetic speedometer, in coinbina tion with a case, a magnet mounted for rotation in the case, a non-magnetic element and ay spindle therefor co-axial with the niagnets rotation; a' frame within the case mounted for movement parallel with said axis and bearings carried thereby for the opposite ends of said spindle; a jack screw mounted for rotation in the case withits axis parallel to the spindle axis; said frame having a threaded aperture to receive the threaded portion of the jack screw and means for rotating the jack screw.

8. In a magnetic speedometer, in combination with a case, a magnet mounted. for rotation in the case; a non-magnetic element and a spindle therefor co-axial with the magnets rotation; a frame within the ease and bearings carried thereby for opposite ends ot' the spindle and comprising hollow posts parallel with the spindle axis; posts fixed in the case on which said hollow posts of the frame are mounted for sliding, and means mounted in the case for so sliding the frame. a

9. In a magnetic speedometer, in combinac tion with a case, a magnet mounted for rotation in the case, a non-magnetic element and a spindle therefor co-axial with the niagnets rotation; a, frame within the case and bearings carried thereby for. opposite ends of the spindle and comprising hollow posts parallel with the spindle axis; posts in the case on which said hollow posts of the frame are mounted for sliding; and a jai-li screw mounted for i'otatioii in the case with its axis parallel lo said last nientioned posts, said frame having a threaded aperture engaged by the thread ol' thc jack screw and iiieans t'or rotating the' jack screw.

In testimony whereof I have hereunto set my hand at Chicago, Illinois, thisl '1st day of July, '1911.

JOHN K. STElVA RT. Vitnesses:

FnxNois W. IAiiiiicii, Jr., EDNA M. MAoIN'iosii. 

